Physiologists have long recognized that the hypothalamus controls the secretory functions of the adenohypophysis with the hypothalamus producing special substances which stimulate or inhibit the secretion of each pituitary hormone. In 1982, human pancreatic (tumor) releasing factors (hpGRF) were isolated from extracts of human pancreatic tumors, purified, characterized, synthesized and tested, which were found to promote the release of GH by the pituitary. Since then, corresponding hypothalamic GH releasing factors from other species and from the human species have also been characterized and synthesized. Human hypothalamic GRF(hGRF) has been found to have the same formula as hpGRF, namely: H-Tyr-Ala-Asp-Ala-Ile-Phe-Thr-Asn-Ser-Tyr-Arg-Lys-Val-Leu-Gly-Gln-Leu-Ser- Ala-Arg-Lys-Leu-Leu-Gln-Asp-Ile-Met-Ser-Arg-Gln-Gln-Gly-Glu-Ser-Asn-Gln-Glu -Arg-Gly-Ala-Arg-Ala-Arg-Leu-NH.sub.2.